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<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Thanks. To be honest, I wasn’t really sure what to do with B0 since there aren’t any modem control lines.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">I just grepped for B0 and looked what other BSPs are doing and they do nothing, so I copied that to have at least common behavior among RTEMS.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b>From:</b> Joel Sherrill <joel@rtems.org> <br>
<b>Sent:</b> Friday, March 5, 2021 6:54 PM<br>
<b>To:</b> Sommer, Jan <Jan.Sommer@dlr.de><br>
<b>Cc:</b> rtems-devel@rtems.org <devel@rtems.org><br>
<b>Subject:</b> Re: [PATCH v3 0/1] Enable baud rate selection for zynq uart<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Fri, Mar 5, 2021 at 11:42 AM Jan Sommer <<a href="mailto:jan.sommer@dlr.de">jan.sommer@dlr.de</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">v3:<br>
- Make sure the baud registers are not modified for baud rate B0<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">B0 is an odd bird. It indicates hang up. From <a href="https://pubs.opengroup.org/onlinepubs/9699919799.2008edition/functions/tcsetattr.html">https://pubs.opengroup.org/onlinepubs/9699919799.2008edition/functions/tcsetattr.html</a>:<o:p></o:p></p>
<p><span style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:black">If the output baud rate stored in the <b>termios</b> structure pointed to by <i>termios_p</i> is the zero baud rate, B0, the modem control lines shall no longer be asserted. Normally,
this shall disconnect the line.<o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:black">If the input baud rate stored in the <b>termios</b> structure pointed to by <i>termios_p</i> is 0, the input baud rate given to the hardware is the same as the output baud rate stored
in the <b>termios</b> structure.<o:p></o:p></span></p>
<p class="MsoNormal"><br>
Since we don't likely have any BSPs which have real modem control <o:p></o:p></p>
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<p class="MsoNormal">lines on the serial ports, that usually means to ignore it so you don't<o:p></o:p></p>
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<p class="MsoNormal">end up with a divide by 0 on the baud rate divisor calculations.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I'm not saying anything negative about your patches. Just that B0 is<o:p></o:p></p>
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<p class="MsoNormal">a weird corner of POSIX and computing history.<o:p></o:p></p>
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<p class="MsoNormal"><br>
v2:<br>
- Use rtems_baud_to_number instead of duplicating baud table<br>
<br>
This patch allows to set the baud rate of the zynq-uart using the termios API.<br>
I could change the baud rate successfully on hardware using the termios application.<br>
<br>
Best regards,<br>
<br>
Jan<br>
<br>
<br>
Jan Sommer (1):<br>
bsps/shared: Allow setting baud rate for zynq uart<br>
<br>
bsps/shared/dev/serial/zynq-uart.c | 21 ++++++++++++++++-----<br>
1 file changed, 16 insertions(+), 5 deletions(-)<br>
<br>
-- <br>
2.17.1<br>
<br>
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